Upgrade python without breaking yum

Question

I recently installed Python 2 7 3 on a CentOS machine by compiling from source  Python 2 7 3 is installed at  opt python2 7 and when I installed it I just changed  usr bin python to point to the new version  This apparently is wrong though because when I did it it broke yum  I would get the following   There was a problem importing one of the Python modules required to run yum  The error leading to this problem was      No module named yum  Please install a package which provides this module  or verify that the module is installed correctly   It s possible that the above module doesn t match the current version of Python  which is  2 7 3  default  May 15 2012  17 45 42    GCC 4 4 4 20100726  Red Hat 4 4 4-13    If you cannot solve this problem yourself  please go to  the yum faq at    http   yum baseurl org wiki Faq   I changed  usr bin python to point back to the python 2 6 6 but now 2 6 6 is the default version of python  Any idea how to fix this

User · Answer

I have written a quick guide on how to install the latest versions of Python 2 and Python 3 on CentOS 6 and CentOS 7. It currently covers Python 2.7.13 and Python 3.6.0:

# Start by making sure your system is up-to-date:
yum update
# Compilers and related tools:
yum groupinstall -y "development tools"
# Libraries needed during compilation to enable all features of Python:
yum install -y zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gdbm-devel db4-devel libpcap-devel xz-devel expat-devel
# If you are on a clean "minimal" install of CentOS you also need the wget tool:
yum install -y wget

The next steps depend on the version of Python you're installing.

For Python 2.7.14:

wget http://python.org/ftp/python/2.7.14/Python-2.7.14.tar.xz
tar xf Python-2.7.14.tar.xz
cd Python-2.7.14
./configure --prefix=/usr/local --enable-unicode=ucs4 --enable-shared LDFLAGS="-Wl,-rpath /usr/local/lib"
make && make altinstall

# Strip the Python 2.7 binary:
strip /usr/local/lib/libpython2.7.so.1.0

For Python 3.6.3:

wget http://python.org/ftp/python/3.6.3/Python-3.6.3.tar.xz
tar xf Python-3.6.3.tar.xz
cd Python-3.6.3
./configure --prefix=/usr/local --enable-shared LDFLAGS="-Wl,-rpath /usr/local/lib"
make && make altinstall

# Strip the Python 3.6 binary:
strip /usr/local/lib/libpython3.6m.so.1.0

To install Pip:

# First get the script:
wget https://bootstrap.pypa.io/get-pip.py

# Then execute it using Python 2.7 and/or Python 3.6:
python2.7 get-pip.py
python3.6 get-pip.py

# With pip installed you can now do things like this:
pip2.7 install [packagename]
pip2.7 install --upgrade [packagename]
pip2.7 uninstall [packagename]

You are not supposed to change the system version of Python because it will break the system (as you found out). Installing other versions works fine as long as you leave the original system version alone. This can be accomplished by using a custom prefix (for example /usr/local) when running configure, and using make altinstall (instead of the normal make install) when installing your build of Python.

Having multiple versions of Python available is usually not a big problem as long as you remember to type the full name including the version number (for example "python2.7" or "pip2.7"). If you do all your Python work from a virtualenv the versioning is handled for you, so make sure you install and use virtualenv!

User · Answer

ln -s  usr local bin python2 7  usr bin python

User · Answer

pythonz  an active fork of pythonbrew  makes this a breeze  You can install a version with     pythonz install 2 7 3   Then set up a symlink with     ln -s  usr local pythonz pythons CPython-2 7 3 bin python2 7  usr local bin python2 7   python2 7 --version Python 2 7 3

User · Answer

I recommend  instead  updating the path in the associated script s   such as  usr bin yum  to point at your previous Python as the interpreter   Ideally  you want to upgrade yum and its associated scripts so that they are supported by the default Python installed   If that is not possible  the above is entirely workable and tested   Change      usr bin python   to whatever the path is of your old version until you can make the above yum improvement   Cases where you couldn t do the above are if you have an isolated machine  don t have the time to upgrade rpm manually or can t connect temporarily or permanently to a standard yum repository

User · Answer

Put  opt python2 7 bin in your PATH environment variable in front of  usr bin   or just get used to typing python2 7

User · Answer

I read a piece with a comment that states the following commands can be run now  I have not tested myself so be careful     yum install -y epel-release   yum install -y python36

User · Answer

If you want to try out rpm packages  you can install binary packages based on the newest Fedora rpms  but recompiled for RHEL6 CentOS6 ScientificLinux-6 on   http   www jur-linux org download el-updates 6    best regards   Florian La Roche

User · Answer

vim  which yum  modify   usr bin python to   usr bin python2 4

User · Answer

Alright so for me  the error being fixed is when there are different versions of python installed and yum can t find a certain  so file and throws an exception  yum wants 2 7 5 according to the error   which python gives me  usr bin python python --version gives me 2 7 5   The fix for me was append  lib64 to the LD LIBRARY PATH environment variable  The relevant content is  lib64 python2 7 and  lib64 python3 6   export LD LIBRARY PATH  lib64  LD LIBRARY PATH   Fixed the yum error for me with multiple python versions installed

User · Answer

Daniel s answer is probably the most ideal one as it doesn t involve changing OS files  However  I found myself in a situation where I needed a 3rd party program which invoked python by calling usr bin python  but required Python 2 7 16  while the default Python was 2 7 5  That meant I had to make usr bin python point to a Python version of 2 7 16 version  which meant that yum wouldn t work  What I ended up doing is editing the file  usr bin yum and replacing the shebang there to use to the system default Python  in my case  that meant changing     usr bin python to     usr bin python2   However  after that running yum gave me an error  ImportError  No module named urlgrabber grabber  I solved that by replacing the shebang in  usr libexec urlgrabber-ext-down the same way as in  usr bin yum  I e       usr bin python to     usr bin python2  After that yum worked  This is a hack and should be used with care  As mentioned in other comments  modifying OS files should be last resort only

[python] Upgrade python without breaking yum

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